Polyester films are widely used as a support for light-sensitive silver-halide photographic materials, on account of its excellent physical properties for that purpose. However, a practical difficulty often arises in the course of attempting to produce and maintain a strong adhesive force between the polyester support and an overlying photographic emulsion comprising a binder such as gelatin, because the polyester film is of a very strongly hydrophobic nature and the emulsion is a hydrophilic colloid.
If the adhesion between the photographic layers and the support is insufficient, several practical problems arise. If the photographic material is brought into contact with a sticky material, such as splicing tape, the photographic layers may be peeled from the support resulting in a loss of image-forming capability. In the manufacturing process, the photographic material is subjected to slitting or cutting operations and in many cases perforated holes are punched into the material for film advancement in cameras and processors. Poor adhesion can result in a delamination of the photographic layers from the support at the cut edges of the photographic material, which can generate many small fragments of chipped-off emulsion layers which then cause spot defects in the imaging areas of the photographic material.
The foregoing property may be referred to as "dry adhesion." This property may be distinguished from "wet adhesion" which refers to the tendency of a photographic element to delaminate during wet processing of exposed film. The element may undergo spot delamination or blistering due to processing at elevated temperatures with typical development solutions or may be damaged by transport rollers during processing or subsequent thereto.
Another variation on this problem is "blocking," which occurs during the manufacturing of the photographic element, when a continuous web coated with the subbing layer is wound in roll form before application of the emulsion layers. In this instance, the front side containing the subbing layer is brought into intimate contact with the coating on the back side, which sides can then stick or block together. This prevents or makes difficult the unwinding of the roll for the application of subsequent coatings.
Various subbing processes and materials have, therefore, been used or proposed in order to produce improved adhesion between the support film and the hydrophilic colloid layer. For example, a photographic support may be initially treated with an adhesion promoting agent such as, for example, one containing at least one of resorcinol, catechol, pyrogallol, 1-naphthol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, 4-chlororesorcinol, 2,4-dihydroxy toluene, 1,3-naphthalenediol, 1,6-naphthalenediol, acrylic acid, sodium salt of 1-naphthol-4-sulfonic acid, benzyl alcohol, trichloroacetic acid, dichloroacetic acid, o-hydroxybenzotrifluoride, m-hydroxybenzotrifluoride, o-fluorophenol, m-fluorophenol, p-fluorophenol, chloral hydrate, and p-chloro-m-cresol.
Polymers are also known and used in what is referred to as a subbing layer for promoting adhesion between a support and an emulsion layer. Examples of suitable polymers for this purpose are disclosed in U.S. Pat. Nos. 2,627,088; 2,968,241; 2,764,520; 2,864,755; 2,864,756; 2,972,534; 3,057,792; 3,071,466; 3,072,483; 3,143,421; 3,145,105; 3,145,242; 3,360,448; 3,376,208; 3,462,335; 3,475,193; 3,501,301; 3,944,699; 4,087,574; 4,098,952; 4,363,872; 4,394,442; 4,689,359; 4,857,396; British Patent Nos. 788,365; 804,005; 891,469; and European Patent No. 035,614. Often these include polymers of monomers having polar groups in the molecule such as carboxyl, carbonyl, hydroxy, sulfo, amino, amido, epoxy or acid anhydride groups, for example, acrylic acid, sodium acrylate, methacrylic acid, itaconic acid, crotonic acid, sorbic acid, itaconic anhydride, maleic anhydride, cinnamic acid, methyl vinyl ketone, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxychloropropyl methacrylate, hydroxybutyl acrylate, vinylsulfonic acid, potassium vinylbenezensulfonate, acrylamide, N-methylamide, N-methylacrylamide, acryloylmorpholine, dimethylmethacrylamide, N-t-butylacrylamide, diacetonacrylamide, vinylpyrrolidone, glycidyl acrylate, or glycidyl methacrylate, or copolymers of the above monomers with other copolymerizable monomers. Additional examples are polymers of, for example, acrylic acid esters such as ethyl acrylate or butyl acrylate, methacrylic acid esters such as methyl methacrylate or ethyl methacrylate or copolymers of these monomers with other vinylic monomers; or copolymers of polycarboxylic acids such as itaconic acid, itaconic anhydride, maleic acid or maleic anhydride with vinylic monomers such as styrene, vinyl chloride, vinylidene chloride or butadiene, or trimers of these monomers with other ethylenically unsaturated monomers. Materials used in adhesion-promoting layers often comprise a copolymer containing a chloride group such as vinylidene chloride.
One commonly practiced process for providing good adhesion of photographic emulsions to polyester supports involves applying an adhesion-promoting layer or subbing layer to the polyester support followed by a coating of gelatin or other hydrophillic colloid material on top of the subbing layer.
Another composition proposed for solving the above-mentioned problem of the weak adhesion force between a polyester support and the emulsion is in Japanese Laid-Open-to-Public Publication No. 11118/1974. A polyester film support is subbed with an aqueous dispersion containing an emulsified copolymer of diolefins and a compound having at least two ethyleneimino groups. Although such a subbing layer was found to have excellent film adhesion characteristics when in a wet state during development treatment and even when in a dry state after drying subsequent to development, nevertheless when such light-sensitive silver-halide photographic materials were processed with an automatic developing machine, wherein the photographic materials were rubbed with a transferring rack or rubber roll of the automatic developing machine, a so-called edge-peel phenomenon was observed, wherein the silver halide photographic emulsion layer were observed to be peeled off from the support at the edges of said photographic materials.
A process intended to overcome the above-mentioned drawback was proposed in Japanese Laid-Open-to-Public Publication No. 104913/1977, wherein a polyester film support was coated with a copolymer of glycidyl methacrylate and ethyl acrylate to form a copolymer sub layer and a gelatin layer comprising colloidal silica was then coated on the copolymer sublayer. A drawback of this process, however, was that a cracking phenomenon was observed in the sublayer under drying treatment with the result that the sub layer thus formed deteriorated in its transparency.
It is also well known to improve the adhesive strength between a layer adjacent to a support and the surface of the support by way of a surface treatment. Examples of these surface activation treatments include, but are not limited to: chemical treatment, mechanical treatment, corona discharge, flame treatment, UV irradiation, radio-frequency treatment, glow discharge, plasma treatment, laser treatment, acid treatment, and ozone-oxidation. Specifics on such treatments may, for example, be found in Hatsumei Kyoukai Koukai Gihou No. 94-6023 and U.S. Pat. No. 5,425,980. Such treatment may be employed with or without the application of a subbing layer.
Some photographic applications require the support to be annealed at high temperatures to provide core set properties, especially smaller sized films (e.g., APS films) utilizing supports made from PEN (polyethylene napthalate). See, for example, U.S. Pat. No. 5,759,756 to Laney et al, which discloses biaxially oriented photographic film supports. Laney et al describes annealing the support while it is wound on a core, at a temperature of from 50.degree. C. up to the lowest Tg of one of the outer layers of film base. Typical annealing conditions for a film base containing a PEN layer are temperatures of from 90.degree. C. to 125.degree. C. for times of 6 to 120 hours. In one example, annealing conditions for samples were 100.degree. C. for 24 hours. The purpose of such annealing is to increase the toughness of the film support and to cause it to resist curl and core set. Laney et al states that the preferred method for promoting adhesion is glow discharge.
In attempting to improve adhesion of films subjected to annealing temperatures, Applicants found that chloride-containing polymers, such as the commonly used vinylidene chloride subbing material, degrade and thereby decrease the adhesion performance of the system, which can cause roll blocking. This material also makes recycling of the support material difficult.
Although apparently experiencing little commercial use, glycidyl-containing polymers have been proposed for improving the adhesion of a light-sensitive emulsion to a polyester support. For example, U.S. Pat. No. 4,328,283 to Nakadata et al. discloses a polyester support on the surface thereof with a subbing layer formed by coating the support surface with an aqueous composition containing a copolymer consisting of the following components: (1) 30-70 wt % glycidyl acrylate and/or glycidyl methacrylate monomer, (2) 3-45 wt % hydroxyalkyl acrylate having an alkyl group of 2 to 4 carbon atoms and/or hydroxyalkyl methacrylate monomer, and (3) 0-67 wt % a copolymerizable vinyl monomer. It was found that wet-film adhesion force was low in the case when less than 30 wt % of the first component was present, and dry-film adhesion force deteriorated when more than 70 wt % was present.
U.S. Pat. No. 3,645,740 to Nishio describes photographic elements that use a blend of gelatin with either a glycidyl methacrylate or glycidyl acrylate homo or copolymer as subbing layers for PET supports. Besides providing adhesion, the coating solutions were found to have good stability and wound coated rolls did not block.
U.S. Pat. No. 4,098,952 to Kelly et al describes a primer for PET supports which contains a copolymer that comprises 3-25 mole % glycidyl (meth)acrylate. U.S. Pat. No. 4,128,426 to Ohta et al describes a subbing layer for photographic film which comprises a copolymer containing 20 to 90% glycidyl (meth)acrylate. U.S. Pat. No. 4,609,617 to Yamazaki et al describes a subbing layer for photographic film comprising a copolymer containing 0.01% to 70% glycidyl (meth)acrylate. GB 1583343 to Mann describes a subbing layer for photographic elements that contains copolymers of acrylic acid or methacrylic acid and their derivatives such as glycidyl (meth)acrylate. GB 2037792 to Kitihara et al describes subbing layers for photographic polyester supports that use copolymers containing 35-55 wt % glycidyl (meth)acrylate. The subbing layer is applied during the manufacturing of the PET (polyethylene terephthalate), and the applied subbing layer is then subjected to corona discharge treatment before applying additional layers. Other patent publications which disclose, in general, the use of a copolymer containing glycidyl methacrylate as a subbing layer for photographic include JP 5134356, JP 59094756, and EP 35614. A research disclosure, RD 18358 1979, describes the use of a butyl acrylate-glycidyl methacrylate-styrene (40-40-20) copolymer as a subbing layer for photography. Notwithstanding the above disclosures, subbing layers comprising glycidyl (meth)acrylic have not experienced widespread commercial application, suggesting that such proposed subbing materials and processes are either not economical and/or do not provide the desired performance characteristics for commercial application.
It is accordingly a primary object of the present invention to provide subbed polyester supports for photographic use wherein excellent film adhesion adhesion to a hydrophilic colloid layer such as a photosensitive emulsion are obtained.